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Development of a Time-Domain Simulation Tool for Offshore Wind Farms
김현규,김관수,백인수,유능수 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie’s eddy viscosity wake model to construct the simulation tool. The wind turbine model also includes an aerodynamic model that is a look up table of power and thrust coefficients with respect to the tip speed ratio and pitch angle of the wind turbine obtained by a commercial multi-body dynamics simulation tool. The wake model includes algorithms of superposition of multiple wakes and propagation based on Taylor’s frozen turbulence assumption. Torque and pitch control algorithms were implemented in the simulation tool to perform max-Cp and power regulation control of the wind turbines. The simulation tool calculates wind speeds in the two-dimensional domain of the wind farm at the hub height of the wind turbines and yields power outputs from individual wind turbines. The NREL 5MW reference wind turbine was targeted as a wind turbine to obtain parameters for the simulation. To validate the simulation tool, a Danish offshore wind farm with 80 wind turbines was modelled and used to predict the power from the wind farm. A comparison of the prediction with the measured values available in literature showed that the results from the simulation program were fairly close to the measured results in literature except when the wind turbines are congruent with the wind direction.
김현규,정주환,이희성,최영룡,정미화 대한마취통증의학회 2010 Korean Journal of Anesthesiology Vol.59 No.-
Lung separation using a double-lumen endobronchial tube is necessary for video assisted thoracoscopy (VATs). Bronchial rupture after intubation with a double-lumen endobronchial tube has been rarely reported. We report a case of a 70-year-old man who had solitary pulmonary nodule in his right upper lobe. He was intubated with a leftsided Robertshaw double-lumen endobronchial tube. He underwent a VATs right upper lobectomy with the one-lung ventilation of left lung. During the operation, the rupture of the left mainstem bronchus was detected. Immediately,the thoracotomy was performed and the ruptured left mainstem bronchus was repaired with absorbable sutures (vicryl). Seven days later he had a bronchoscopy to examine the left mainstem bronchus. There was no evidence of the bleeding, leakage and inflammation. Subsequent course was uneventful. Tracheobronchial injuries related to the double-lumen endobronchial tube are discussed.
Electronic band structure of Pb-substituted layered perovskite materials
김현규,장점석,지상민,배상원,이재성 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
Perovskite-type oxide materials based on transition metals with d(0) electron configration such asNb(V), Ta(V), and Ti(IV) are efficient photocatalysts for overall water splitting with high quantum yields. However, the band gaps of these materials (ca. 3.8-4 eV) are not adequate for visible lightinduced photocatalysis. The development and fabrication of materials showing photocatalytic activity for water splitting into H2 and O2 and degradation of organic pollutants under visible light irradiation, therefore, is the most important topic in the photo-catalysis research today. In the present study, band gaps of Pb-substituted layered perovskite materials were investigated using Full Potential Linerarized Augmented Plane Wave (FLAPW) method.
김현규,노환중,구수권,송창윤,한철우,김성원 대한이비인후과학회 2005 대한이비인후과학회지 두경부외과학 Vol.48 No.8
Background and Objectives:The objective of this article is to evaluate the effectiveness and the compliance rates of immunotherapy, and to identify the factors affecting the compliance of immunotherapy. Subjects and Method:We evaluated the charts of 120 patients with allergic rhinitis and/or asthma, for which allergen immunotherapy was carried out from 1998 and 2000. Information was obtained via chart reviews and telephone surveys. Results:Among the 120 patients with allergic rhinitis, 41 patients also had asthma. The common allergens identified by the skin prick test prior to immunotherapy were D. farinae, D. pteronyssinus, dog fur, cat fur, and cockroaches, et al. The skin prick test reactivity to common allergens is significantly lower after three years of immunotherapy than it is prior to immunotherapy. The satisfaction of patients after immunotherapy between the allergic rhinitis group and allergic rhinitis with asthma group are as follows:much satisfied (25.4%/27.3%), fairy satisfied (31.6%/33.7%), a little satisfied (15.2%/17.2%), not satisfied (17.1%/13.3%), and unsure (10.7%/8.5%). In our study, the compliance rates of immunotherapy were 65.7%. The reasons cited for discontinuance of allergen immunotherapy were inconvenience (45%), lack of improvement in symptoms (23%), improvement in symptoms (15%), greater improvement in symptoms through medication (11%), and other reason (7%). Conclusion:If we increase the compliance of immunotherapy through various researches on the compliance of immunotherapy and educating patients about it, allergen immunotherapy may become more effective in treating allergic disorders.